harmonious vs harmoniousness

harmonious is not a noun while harmoniousness is a noun.

Word	Noun	Adjective	Verb	Adverb
harmonious	No	Yes	No	No
harmoniousness	Yes	No	No	No

harmonious (noun)	harmoniousness (noun)
	compatibility in opinion and action
	the property of sounding harmonious

harmonious (adjective)	harmoniousness (adjective)
musically pleasing
exhibiting equivalence or correspondence among constituents of an entity or between different entities
existing together in harmony
suitable and fitting